Plague… it’s a term that typically conjures up images of the devastating "Black Death", the pandemic that killed 75-200 million people in Europe back in the 14th century. Yet, it’s not just a historical disease. Plague is still present in a variety of small mammals in different regions worldwide (see map), including parts of the US, with periodic reports in Canada.

A recent case of plague in a Colorado man has attracted a lot of attention.  The individual developed the pneumonic form of the infection after his dog died of the same disease. It’s suspected that he was infected from a flea that fed on the infected dog, and then bit the man. However, I don’t think you can really rule out the potential for direct transmission of the bacterium, Yersina pestis, from the dog. Fortunately, despite developing pneumonic plague (the form in which the bacterium infects the lungs, and the deadliest form of Y. pestis infection), it seems that he’s recovering.  Plague is treatable with antibiotics, but it is critical that treatment be started as soon as possible or it can be fatal.

Transmission of plague from pets to people isn’t new. However, most often it involves cats that get infected while hunting rodents carrying infected fleas. Cats can develop plague, and then people caring for them (e.g. owners, veterinarians) can acquire the infection.

This case highlights a few important points:

  • Plague is still around. People living in areas where plague is present need to be aware of the risk, even though it’s very low.
  • Pets get infected from contact with infected rodents, either directly or from their fleas. Keeping pets away from wildlife (e.g. keeping cats indoors, limiting free-roaming of dogs) can reduce the risk of exposure.
  • Sometimes, knowing the cause of an animal’s illness is very important for human health. Knowing that a pet had plague would greatly speed up consideration of plague in anyone who became sick and had contact with the animal.
  • Flea control can help reduce the risk of many diseases, including plague.

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